Seems to be a running theme, but how do you know when you're done block sanding?

[jtfx6552]

I blocked my mustang doors. I think they're straight. 2K doesn't shine so it's hard to see any reflection, so I wet them down with water and looked at the reflection of the ladder on the wall. Looks straight, I think?

 

[dhutton01]

If you use a guide coat there will be no guessing imho. I like the 3M dry guide coat.

Don

 

['68 Coronet R/T]

If you use a guide coat there will be no guessing imho. I like the 3M dry guide coat.

Don

Agree!

Below is my second full restoration of a classic car and the first time I ever used 3M Dry Guide coat. I was so impressed with it that I took some pictures.
Here you can see the guide coat being removed. To get panels straight you want to use a coarse grit on the longest block that will fit.

Here you can see there are still low spots. These are small imperfections that will come out with more sanding.

I have black epoxy primer under the 2k primer. The process may require more 2k primer being applied if you start to see the epoxy primer showing through and still have low spots like above showing.

Finished:

 

[Rbm]

When the wife screams we're gonna be late.

 

[clubairth]

Yes the change to dry guide coat was a good one!
Quicker too. No waiting for paint to dry.
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[MikeK]

Just don't leave it Outside,
Not exactly "water soluble".

 

[Lizer]

Did you use guide coat?

When your guide coat sands completely off uniformly is your answer.

When my guidecoat sands completely off, I guidecoat one more round and block again.

 

[shine]

Pounce powder. Cheaper.

 

[LITJOHN]

All I've ever used as a guide is a very light coat ( mist ) of blue layout fluid. I liked it but on the next one I'm going to try some other product. I guess a bit of both, 3m and pounce and see how it goes.

 

[metalman]

I have used over reduced black basecoat, over grey 2K, speckled or dusted on. Safer IMO that a rattle can.
I do plan to try dry guide coat, have black pounce powder which is charcoal IIR.

 

[shine]

3m is just overhyped and overpriced pounce powder. true pounce powder is finer and spreads better.

 

[theastronaut]

Mirka dry guide coat is a much better deal than 3M.

 

[clubairth]

I have heard this before but where do you find pounce powder? I know it's used for sewing patterns as my Mom had a pounce bag when I was growing up.
I also use a wide black marker usually on bare metal.
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['68 Coronet R/T]

Just don't leave it Outside,
Not exactly "water soluble".

That's what makes it good for final wet sanding as well.

 

[jtfx6552]

3m is just overhyped and overpriced pounce powder. true pounce powder is finer and spreads better.

Is this it?

https://www.amazon.com/Hancy-2-Ounce-Ultimate-Pounce-Powder/dp/B000JS55OY/ref=sr_1_6?crid=WT8775GWEAU9

 

[metalman]

I have heard this before but where do you find pounce powder? I know it's used for sewing patterns as my Mom had a pounce bag when I was growing up.
I also use a wide black marker usually on bare metal.
.
.
.

Used to be a standard item at any sign supply. Not used much anymore. We would put it in a cotton cloth with some cotton balls, tie it up into a bag and wack it against the sign pattern to transfer the lines. Also did the same thing with blue carpenters snap line chalk to show up on dark surfaces.
Quick check found this: https://letterheadsignsupply.com/black-pounce-powder. Search charcoal pounce powder.

 

[metalman]

Sill have a little from waaay back. got me doing the nostalgia thing.

 

[shine]

hobby shops or amazon. kit will have an applicator with it. mine is so old it has a wooden box . lid has a pad on it and the powder goes in the box. still have all my pounce spur wheels. great for doing flame jobs on hoods.

 

[MikeK]

That must be Good stuff metalman,

It's for Signwriters,
Not Signpainters.....

There was a Sign shop next to my dads shop back in the 60's and I use to go over and watch them letter trucks. Had paper masking with all these tiny holes taped on and dusted the paper with the 'bag' and removed the paper and vol-ah instant outline. Man,those guys were unreal watching them paint.Even with the outline,you had to be good at it.I know,I tried it.

 

[shine]

i bought this in the early 70's. nasty looking because it went through the fire in 94 . the pad is shot. rotten from age so i need to put a new sponge in it. i really dont use it anymore. i use a jersey cotton glove instead.